BMP280 pressure with if condition

Other Hardware Sensors
1

Hi guys, i’m trying to use a BMP280 with LED and want to add if condition with pressure, but it is not working ..can you please suggest how to fix this.

My code is:

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_BMP280.h>

#define BMP_SCK  (13)
#define BMP_MISO (12)
#define BMP_MOSI (11)
#define BMP_CS   (10)
const int ledPin =  13;  
Adafruit_BMP280 bmp; // I2C
//Adafruit_BMP280 bmp(BMP_CS); // hardware SPI
//Adafruit_BMP280 bmp(BMP_CS, BMP_MOSI, BMP_MISO,  BMP_SCK);

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);


  if (!bmp.begin(0x76)) {
    Serial.println(F("Could not find a valid BMP280 sensor, check wiring!"));
    while (1);
  }

  /* Default settings from datasheet. */
  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,     /* Operating Mode. */
                  Adafruit_BMP280::SAMPLING_X2,     /* Temp. oversampling */
                  Adafruit_BMP280::SAMPLING_X16,    /* Pressure oversampling */
                  Adafruit_BMP280::FILTER_X16,      /* Filtering. */
                  Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */
}

void loop() {


    Serial.print(F("Pressure = "));
    Serial.print(bmp.readPressure()/100);
    Serial.println(" Pa");
    Serial.print(pressure); //  mm Mercury
float pressure = bmp.readPressure() * 0.00750061683;

  if ((pressure * 0.00750061683) >981.70)
  {
    // Pressure too high
    digitalWrite(ledPin, LOW);
  }
    
if ((pressure * 0.00750061683) <981.70)
  {  // turn LED off:
    digitalWrite(ledPin, HIGH);
  }
}
2

What does [quote="abhixs, post:1, topic:1043269"]but it is not working[/quote] mean?

What is this supposed to do float pressure = bmp.readPressure() * 0.00750061683; and why do this pressure * 0.00750061683 in the if?

3

Which Arduino board are you using ?
How precise do you expect a float to be when using that board ?

Why are you multiplying pressure by 0.00750061683 and why are you doing it twice ?

4

I am using Arduino nano.
it can be precise between 4-5 digit

by mistake i used 0.00750061683 twice, i was looking some examples on google and i copy pasted code from there. I don't have so much idea about this sensor.

5

So, post your updated code and tell us what you mean by "not working"

I don't suppose that you have tried printing the value that you are testing to see whether it looks reasonable, or have you ?

6

Hello
Run this tutorial to gain the knowledge.

7

If condition for LED is not working, i mean when pressure is <981.70 led is not getting on and when pressure is >981.70 led is not getting off.

Updated Code:

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_BMP280.h>

#define BMP_SCK  (13)
#define BMP_MISO (12)
#define BMP_MOSI (11)
#define BMP_CS   (10)
const int ledPin =  13;  
Adafruit_BMP280 bmp; // I2C
//Adafruit_BMP280 bmp(BMP_CS); // hardware SPI
//Adafruit_BMP280 bmp(BMP_CS, BMP_MOSI, BMP_MISO,  BMP_SCK);

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);


  if (!bmp.begin(0x76)) {
    Serial.println(F("Could not find a valid BMP280 sensor, check wiring!"));
    while (1);
  }

  /* Default settings from datasheet. */
  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,     /* Operating Mode. */
                  Adafruit_BMP280::SAMPLING_X2,     /* Temp. oversampling */
                  Adafruit_BMP280::SAMPLING_X16,    /* Pressure oversampling */
                  Adafruit_BMP280::FILTER_X16,      /* Filtering. */
                  Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */
}

void loop() {


    Serial.print(F("Pressure = "));
    Serial.print(bmp.readPressure()/100);
    Serial.println(" Pa");

float pressure = bmp.readPressure() * 0.00750061683;

  if ((pressure) >981.70)
  {
    // Pressure too high
    digitalWrite(ledPin, LOW);
  }
    
if ((pressure) <981.70)
  {  // turn LED off:
    digitalWrite(ledPin, HIGH);

}}
8

You are still not printing the value that you are testing and have not said what "not working" means

Please help us to help you

9

Why is the pressure reading being multiplied by 0.00750061683?

Have you done a

float pressure = bmp.readPressure() * 0.00750061683;
Serial.println( pressure );
  if ((pressure) >981.70)

to see what the result is?

10

this value i am getting printed

sssss
sssss999×720 144 KB

11

981.70*0.00750061683 = 7.363355542011, quite strange. Also, the LED will not come on. Try removing the *0.00750061683 part.

I've not ever experienced a BMP or BME giving such stable pressure readings as shown in post#10.

12

Thank you so much, this solved my problem ..thanks a lot again :slight_smile:

1 Like
13

What solved your problem?

14

This solved my problem :slight_smile:

float pressure = bmp.readPressure() * 0.00750061683;
Serial.println( pressure );
  if ((pressure) >981.70)
15

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